Lithographic process



Patented July 24, 1951 LITHOGRAPBIC PROCESS James Finno, Brooklyn, N.Y.

No Drawing. Application February 3, 1947,

Serial N0. 726,197

(Granted under the act of March 3, 1883. as

' amended April 30, 1928; 370 O. G. 757) 19 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without payment to me of anyroyalty thereon.

This invention relates to a planographic offset printing process andmore particularly to an improvement in parchment planographic printingplates, an improved etching solution for preparing such plates forprinting and an improved dampening solution for application to theparchment plates when employed in planographic duplicating machines.

This application is in part a continuation of application Serial No.596,718, filed May 30. 1945, now abandoned.

The standard commercially available equipment for carrying out theprocess of planographic offset printing consists, briefly, of aduplicating machine provided with an impression cylinder, 9. moisteningroll, an inking roll and a rubber transfer cylinder. A planographicprinting plate having an ink receptive image formed on the surfacethereof in any suitable manner is mounted on'the impression cylinder.During rotation of the impression cylinder the printin plate first comesinto contact with the moistening roll which is saturated with aninkrepellent solution. The property of the nonimage portion of thesurface of the printing plate is such that it is uniformly wetted by theinkrepellent solution, while the ink formin the image portion of theprinting plate is unwetted by the solution. As the impression cylindercontinues to rotate, the printing plate comes into contact with theinking roll which applies a lithographic or grease base type of ink tothe image on the printing plate. The non-image portion of theprintingplate previously wetted with an ink-repellent solution will not pickupthe ink. Further rotation of the impression cylinder. brings theprinting plate into contact with a rubber transfer roll which acceptsthe ink from the entire image. The transfer roll is then rotated over asheet of paper and the ink portions which correspond to the originalimage are deposited upon the paper to provide a final copy.

The printin plates employed in the process outlined above were, in theearlier stages of development of the process, photographically preparedmetal or cellulose plates. While such plates were, and still are,satisfactory, the cost thereof and the expense of preparing them areobvious disadvantages. In recent years, the trend has been to replacesuch plates by employing paper printing plates or masters and totievelop simple, direct-and inexpensive methods of formin an image onthe surfaces thereof. This trend is illustrated by the patents grantedto William B. Wescott, Patent No. 2.134.165, dated October 25, 1938,Patent No. 2,205,998. dated June 25, 1940; and Patent'No. 2.348.771,dated May 16. 1944. These patents are directed generally to a compositepaper printing plate consisting of layers of cellulosic materialadhesively or otherwise bonded. One of the layers which serves as aprinting surface is formed from a dense amyloid parchment paper. Theremaining layer is formed from a heavy, water-repellent paper and servesas a backin or support for the water-absorptive parchment layer. More Irecently a patent granted to Arthur Garrett, Patent No. 2,363,311, datedNovember 21. 1944. disclosed an unbacked printing plate formed fromsupercalendered amyloid parchment paper. Images may be formed on theseprinting plates by the simple expedient of depositing an imageformin inkthereon with a pen or pencil but preferably with a typewriter providedwith a ribbon saturated with an image-forming ink. The paper printingplates thus prepared for printing on an offset duplicating machine areusually treated with ink or scum-displacing solutions since plates ofthis type are easily smudged either in handling or during the printingoperation. These scum-removin compositions usually comprise aqueoussolutions of glycerine and contain small quantities of phosphates andgum arabic. The chemistry of the action of such solutions has beenthoroughly studied and it is known that, heretofore solutions of thistype did not improve the quality of the image, per se. In addition toscum-removing solutions it has been necessary to employ dampening orfountain solutions with these plates to render the non-image portion ofthe printing plate ink-repellent. Such solutions consist essentially ofaqueous .solutions of glycerine and are applied to the plate withmoistening rolls as previously described.

The foregoing paper printing plates have met with commercial success butare. albeit, subject to numerous objections. The multi-ply type of paperprinting plates are expensive and un-. economical for preparing a smallnumber of copies; The composite .or multi-ply printing plates lackflexibility and may not be erased satisfactorily. It has been found thatmultipiy' printing plates which have been erased will. upon beingmoistened with standard ink-repellent solutions. demonstrate swelling inthe areas which have been erased with the result that imagessubsequently applied to the erased areas are broken by distension orbucklin of the swollen surface. In the case of single-plysupercalendered amyloid parchment plates erasures produce a similar typeof failure. This latter action is not understood but it is believed thatsupercalendering forms a tough skin on the surface of parchment paper sotreated which is broken by the erasing action and that when the latteroccurs the fibers, which are uncoated or the coatings of which have beenbroken, absorb water and swell. Aside from the above obJections, theprincipal disadvantages which both multi-ply composite sheets andsupercalendered sheets have been found to possess lies in the lack ofpermanency of the images formed thereon.

This has been found to be due to the surface characteristics of thepaper employed and not merely to any property of the image-forming inkused. For example, various commercially available image-forming inkshave been applied to both multi-ply sheets and supercalendered parchmentsheets and it has been determined that such plates will last in storageno longer than approximately three days at which time the images werefound to have disintegrated completely and become useless. The imagesformed on such plates. furthermore, failed to last as long as the paperprintin plate upon which they were deposited when employedimmediately-following preparation in an offset printing process.

This invention is an improvement over the inventions disclosed in theabove patents and is based essentially on the use of a single-ply,unsized and substantially uncalendered parchment paper in forming theplanographic printing plate. The plates are thus formed of aninexpensive parchment paper stock which is not coated with any sizingmaterial, does not contain any fillers, pigments or the like whichincreases the transparency and, furthermore, requires no backing orsupport. The parchment paper stock employed must be substantiallyuncalendered for the purposes of this invention since the absence ofcalendering imparts flexibility to the plate formed therefrom andprovides a slightly rough surface which possesses an afllnity forimage-forming ink not heretofore demonstrated by any paper planographicprinting plate. The lack of calendering of the parchment paper stock,furthermore, provides a printing plate which may be erased with aminimum loss of the original surface characteristics of the plate. Theuse of these parchment plates in standard duplicating or printingmachines is limited, however, in that the dampening solution forming apart of this invention must be employed therewith to produce the desiredresult and, if the use of a scum-removing etching solution is desired,only the etching solution forming a part of this invention may be usedin conjunction with the parchment plates and dampening solutionsdisclosed herein.

The etching or scum displacing solutions forming a part of thisinvention are applied to the plates in the usual manner prior to, theiruse in the printing process. The etching solution consists of an aqueoussolution of glycerine and preferably a minor amount of sodium sulfate.The most essential components of the solution, however, are sodiumthiosulfate and citric acid. A minor portion of these latter ingredientsare dissolved in equal quantities in the solution and serve to impartpermanency to the printing plate image. The dampening solution whichforms a part of this invention consists of glycerine, a

small amount of gum acacia and as essential ingredients small amounts ofsodium sulfate and boric acid dissolved in water. This solution isapplied to the printing plate by the moistening roll of the duplicatingmachine and renders the non-image portion of the uncalendered parchmentplate ink-repellent without causing swelling or buckling.

As an additional feature, the parchment plates of this invention may beprovided with a preprinted image on the printing surface thereofconsisting of a quick drying synthetic resin base ink. This image may beapplied simply with a metal offset planographic printing plate and theimage formed dries without offset practically instantaneously. Imprintsof marginal scales or other guides may be applied to the reverse side ofthe printing plate as a reversed image employing a water soluble orother printing or nonprinting ink. The transparency of the parchmentpaper plate permits the reversed image on the non-printing face of theplate to be viewed through the body of the plate from the printingsurface thereof and thus provides a visual copy layout guide in the formof an unreversed or normal image.

It is, therefore, the principal object of this invention to provide aninexpensive flexible cellu losic planographic printing plate formed of asingle ply, unsized, unbacked, and substantially uncalendered amyloidparchment characterized by low gloss and low smoothness.

Another object of this invention is to provide an unbacked,substantially uncalendered parchment planographic printing plate havingan image-forming ink deposited thereon which may be stored for extendedperiods of time without image deterioration or loss of the printingquality thereof.

Another object of the invention is to provide a single-ply,substantially uncalendered parchment printing plate having a pre-printedimage formed from a quick drying synthetic resin image-forming ink.

Another object of this invention is to provide a single-ply,substantially uncalendered parchment printing plate which may be erasedwithout altering the original surface characteristics of the plate.

Still another object of this invention is to provide a quick drying,image-forming synthetic resin ink which may be applied to a single-ply,substantially uncalendered parchment printing plate by standard offsetmethods without spreading or feathering.

A further object of this invention is to provide a planographic printingplate scum-removing etching solution which has the property of hardeninglithographic image-forming ink to impart permanency thereto withoutdamaging the printing plate.

A further object of this invention is to provide a planographic printingplate etching solution which is non-toxic and non-irritating to skin andwhich is characterized by the property of removing scum and inkblemishes'upon direct application to the printing plate or of forming acoating upon the plate from which scum and ink blemishes may be easilyremoved merely by the normal application of a fountain solution thereto.

A further object of this invention is to provide an etching solution forplanographic printing plates which will not coat the image portion ofthe plate and will, upon application to metallic planographic printingplates, etch the non-image portion thereof, thereby improving theclarity of the image portion,

A still further object of this invention is to provide'a dampeningsolution for use with singleply, substantially uncalendered parchmentprinting plates which will render the non-image portion of the platesink-repellent without causing distension of the-plate.

It is furthermore, an object of this invention to provide a dampeningsolution for use with a single-ply, substantially uncalendered parchmentprinting plate which is characterized by the property of producing anevenly distributed film of water on the non-image surface of the plateto render it ink-repellent but which will not saturatethe body oftheplate and from which. film the water evaporates sufiiciently rapidlyto prevent water from puddling on the plate surface.

The parchment planographic printing plate comprising this invention isprepared from parchment paper produced from high alpha cellulose pulp inthe following manner. A waterleaf prepared from the pulp as a web on apaper making machine in the usual manner is 'sub jected to the action ofsulfuric acid under controlled conditions.- The cellulose fibers or thesurfaces thereof are gelatinized by thesulfuric acid to produce asubstance known in the art asamyloid. The fibers of thepaper are thusattacked by the acid which forms a coating or film of gelatinouscellulose, covering the fibers and filling the interstices of the sheet,cementing or bonding the fibers into a coherent mass. Subsequently theexcess acid is removed from the paper by both physical and chemicalaction and the web thereafter passed through drying rolls.

6 desired translucency of the paper is enhanced by omitting fillers andpigments.

The parchment paper made as above described and possessing the foregoingproperties provided with marginal scales and other lay-out The web ispreferably not calendered within the industrial meaning of the term, or,if so, only slightly." While the art has heretofore recognized that theimpression factor of paper printing plates increases with an increase inthe gloss and degree of calendering of the paper stock from which theplates are formed, contrary to this teaching the invention herein ispredicated upon the use of a parchment paper stock, the surface of whichis characterized by a minute grain finish similar to fine grain groundglass. The parchment paper stock must also possess low gloss and lowsmoothness values. The paper produced in the manner above describedshould have a smoothness measure of less than approximately seconds whentested on a Bekk smoothness tester and preferably a smoothness measureof from 10 to 15 seconds. The gloss of this paper should beappromixately 25.0 per cent when measured in an Ingersoll Glarimeter.The weight of the parchment paper may vary from to 110 pounds per ream(500 sheets. 24 x 36) but it is preferred to employ a paper having aweight of approximately 60 pounds per ream (500 sheets, 24 x 36). Thethickness of the paper varies according to the weight but in the case ofpaper having a weight of 60 pounds per ream the thickness should beapproximately .0035". Regardless of the weight per ream this parchmentpaper possesses very nearly uniform texture throughout itscross-section. Owing to the lack of calendering it is highly flexibleand it does not possess a high machine finish but rather a fine grainfinish which does not differ materially'from the texture of the paperbeneath the surface. This characteristic is furthermore insured byexcluding the use of paper sizes. The

guides formed by printing such material in the form of a reversed imageon the non-printing face of the plate. Owing to the translucency of theplate, such images are visually perceptible as normal images throughjtheplate from the printing surface thereof.

It has been found especially desirable to prepare preprintedplanographic printing plates of parchment paper. Thus, oflices employingstandard forms'such as contracts, leases, lists or the like have a needfor a printing plate having standard clauses, tables and columnspreprinted thereon and to which a typist may add additional specialinformation with a standard image forming ink. Parchment printing platesso prepared may be used in duplicating machines to provide a largenumber of copies of both the preprinted portion and the subsequentlyapplied indicia. An image forming ink suitable for preparing preprintedparchment printing plates has been developed which comprises an oilmodified phenol-formaldehyde resin, partially polymerized linseed oil,polymerized linseed oil gel, driers and pigments. One ink compositionwhich has been found to give satisfactory results appears in thefollowing example:

Example Parts by weight Alkali blue-oil modified phenol-formaldehyderesin dispersion 40 Iron blue-No. 1 lithographic varnish dispersion 10Lead tetroxideNo. 3 lithographic varnish dispersion 20 Metallic soapdrier-polymerizable oil dispersion 20 Polymerized linseed oil gel havinga viscosity substantially equal to that of a. #5 varnish 10 Theforegoing may be prepared by mixing the Alkali blue and oil modifiedphenol-formaldehyde resin in the proportion of 3 parts to 5 parts byweight respectively. The Iron blue pigment is mixed in equal parts byweight with No. 1 Lithographic varnish which is a commercially availableoil consisting of partially polymerized linseed oil. The numericaldesignation of the oil indicates the degree of polymerization thereofand as the numerical designation increases the oil identified thereby ismore completely polymerized. The lead tetroxide and No. 3 Lithographicvarnish are mixed in the proportion of 5 parts to 1 part by weightrespectively. The metallic soap drier may be any of the common driers ofthis type available on the market such as cobalt linoleate or a mixtureof lead and manganese soaps and are employed in small amounts dispersedin polymerizable oils. The polymerized linseed oil gel is a thickenerand consists of a partially polymerized linseed oil mixed with a soap,which serves as a gelatinizing agent.

The proportions of the various ingredients may be varied according tothe distribution and transfer required by a specific printing operation.Thus, the oil vehicles are increased if greater distribution andtransfer are required. The synthetic resin binder employed may be anyoil modified phenolic or alkyd type of resin which is quick drying. Theink sets as a result of both polymerization and oxidation and the ratethereof may be controlled by the amount and type of driers employed. Theink prepared in the manner described above may be applied toplanegraphic parchment printing plates by offset printing methods,preferably by means of planographic metal printing plates. The imagesformed on the parchment plates dry practically immediately withoutoffset. If necessary, the drying time may be reduced by warming thepreprinted parchment plates slightly. The images thus formed are lastingand the preprinted parchment plates may be stored for from 6 months toone year without loss of the printing quality of the image. The samelasting quality of images formed from standard rease-base image forminginks is obtained with the uncalendered parchment printing platesdescribed above; It is believed that this property is due to the surfacecharacteristics of the plate and that the presence of a minutely fibroussurface on the uncalendered printing plate protects the images depositedthereon from failure due to abrasion as well as to oxidation.

Theetching solution forming a part of this invention is especiallyadapted for use with the uncalendered parchment printing platespreviously described. These solutions perform not only the function ofremoving or displacing ink scum blemishes from the non-image areas ofthe printing plates but also act as hardening agents for grease-basetype of image forming inks. The etching solution comprises an aqueoussolution of glycerine, sodium sulfate and equal amounts by .weights ofsodium thiosulfate and citric acid. On the basis of a gallon of solutionit is preferred to use one ounce each of sodium thiosulfate and citricacid. These quantities may be increased up to four ounces each of thecitric acid and sodium 'thiosulfate, equal amounts by weight thereofalways being employed. More than four ounces each of these ingredientstend to destroy the image on the printing plate rather than to hardenand preserve it. The glycerine content of a gallon of the solution maybe varied from 1 to 64 ounces by volume. It is preferred to employapproximately ounces of glycerine. If the glycerine content is increasedabove 64 ounces it has been determined that the sensitivity of theprinting image to the lithographic ink is retarded. The quantity ofsodium sulfate may be varied from 1 to 8 ounces per gallon of solutionwith 2 ounces being the preferred quantity. If more than 8 ounces ofsodium sulfate are employed, the action resulting from the combinationof sodium thiosulfate and citric acid is neutralized. In the foregoingcomposition glycerine functions as a wetting agent while the sodiumsulfate serves to impart a soapy texture to the surface of the printingplate and distributes the etching solution over the printing platesurface. The sodium thiosulate and citric acid react to produce free SO:which imparts hardness to the grease-base type of image forming ink.This hardening effect lengthens the life of image and improves theprinting quality thereof.

The etching solution is applied to the parchment printin plate by pourinthe solution over the surface of the plate after the image has beenapplied thereto and is then gently spread over the surface of the platewith a cotton swab. Any blemishes such as finger smudges or ink stainsdeposited during the preparation of the plate for printing are eitherremoved or loosened. Simultaneously the sodium thisoulfate and citricacid harden the grease base image forming ink. The plate may be placedon the impression cylinder immediately and the printing processcommenced. Any blemishes which have been displaced by the etchingsolution during its application are removed by the fountain solution.The coating formed on the surface of the printing plate by the etchingsolution is such that ink scum blemishes which aredeposited on thesurface of the plate during theprinting operation are likewise removedby the fountain solution.

The etching solutions described above may also be applied to metalplanographic printing plates having image forming inks on the surfacethereof. In addition to functioning as an ink scum blemish removingagent the sodium thiosulfate and citric acid actually etch the areas ofthe printing plate adjacent the ink image. This causes the image tostand out above the nonprinting surface of the plate and materiallyimproves the printing quality of such plates. The etching solutions,furthermore, do not coat the image which is a distinct advantage inmetal plates having a half-tone or shaded image.

The dampening or fountain solutions forming a part of this invention areespecially developed for rendering the non-image area of theuncalendered parchment printing plates described above ink-repellent.The solutions comprise glycerine, sodium sulfate. boric acid and gumacacia dissolved in water. In lieu of sodium sulfate, calcium chloride,1 to 16 ounces, may be used in the solutions. However, it demonstrates atendency to remain on the image portion of the plate and will.ultimately, produce light colored copies. On the basis of one gallon ofsolution the glycerine content may vary from 10 per cent or 12.8 ouncesto per cent or 64 ounces by volume. It is preferred to employ 64 ouncesof glycerine in solutions for dampening plates formed from parchmentpaper having a weight of pounds per ream (500 sheets. 24 x 36). Theglycerine content of the solutions may be decreased to the lower limitof 12.8 ounces in dampening printing plates formed from heavier stock;as, for example, weights ranging from 60-110 pounds per ream (500sheets, 24 x 36). The sodium sulfate (calcium chloride) content of thesolutions may vary from 1 to 16 ounces per gallon of fountain solutionwith from 1 to 8 ounces per gallon being the preferred range. The rangeof from 1 to 8 ounces of sodium sulfate produces uniform heavy blackcopies throughout the entire run while amounts in excess of this rangeproduce progressively lighter copies. In a solution for dampening platesformed from parchment paper having a weight -of 60 pounds per ream (500sheets, 24 x 36) a sodium sulfate content of 6 ounces per 'gallon hasbeen found satisfactory. The boric acid content may range from i to 6ounces per gallon of solution and produce the desired result. A boricacid content of approximately 2 ounces per gallon of solution ispreferred. The gum acacia is employed in small amounts usually /4 to 3ounces per gallon of solution. The glycerine functions as in fountainsolutions previously employed in this field. The sodium serves, as inthe case of the etching solutions described above, to distribute thesolution over the surface of the plate. The most important relationshipbetween the several ingredients of the fountain solution exists betweenthe sodium sulfate and the boric acid. The former tends to distributemoisture over the surface of the parchment printing plate. Therelationship is such that during each rotation of the impressioncylinder the concentration and distribution of water on the surface ofthe printing plate is suilicient to render the non-image portionsthereof thoroughly ink-repellent without the plate being saturatedwhereas the rate of evaporation is suillciently great that, duringtheinterval between the transfer of the ink from the printing plate tothe rubber transfer cylinder and the remoistening of the plate, thegreat bulk of the water content of the solution is removed from thesurface of the printing plate. This, in effect, prevents water frompuddling on the surface of the printing plate and overcomes any tendencyof the plate to swell or buckle.- The foregoing phenomenon is so markedthat commercially available fountain solutions and the fountain solutiondescribed above may be deposited in thin films on an uncalenderedparchment plate and, while the former solutions will saturate theprinting plate substantially instantaneously, the latter will remain onthe surface for several minutes without saturating the plate.

The fountain solutions described above are essential in offset printingprocesses in which the uncalendered parchment printing plates disclosedabove are employed. The use of any other fountain solution results indistension of such plates as well as the destruction of the imagethereon. Furthermore, these fountain solutions can be employed only withthe etching solution described above. If commercially available etchingor scum-removing solutions are used in conjunction with these fountainsolutions the images on the printing plates are broken. However, theetching solutions and fountain solutions may be employed in printingprocesses involving the use of printing plates of any other type.

The advantage of the process is apparent from the results of tests mayunder many conditions which indicate that a single-ply, unsized anduncalendered parchment planographic printing plate may be employed in aduplicating machine along with the fountain solutions described toproduce over 3000 clear, deep black copies. Furthermore, the etchingsolutions and fountain solutions described herein have been employed induplicating machines using commercially available multi-ply planographicprinting plates with the result that the output thereof has beenincreased from approximately 3000 copies to over 10,000 copies.

Having thus described my invention, what I claim as new and wish tosecure by Letters Patent is:

1. A combined ink scum removing and grease base ink hardening etching,composition for planographic printing plates comprising, in thefollowing proportions, 1 to 64 ounces of glycerine by volume, 1 to 8ounces of sodium sulfate, 1 to 4 ounces of sodium thiosulfate, 1 to 4ounces of citric acid and suflicient water to prepare one gallon ofsolution, said sodium thiosulfate and 10 base ink hardening etchingcomposition for planographic printing plates comprising 20 ounces ofglycerine by volume, 2 ounces of sodium sulfate, 1 ounce of sodiumthiosulfate, 1 ounce of citric acid and suflicient water to bring thevolume of the solution up to one gallon.

3. A method of treating a planographic printing plate having an imagethereon formed from a grease base type of ink which comprises the stepof applying an aqueous solution of 20 ounces of glycerine by volume, 2ounces of sodium sulfate, -l ounce'of sodium thiosulfate, 1 ounce ofcitric acid, and sufficient water to make one gallon of solution, to thesurface of said plate for simultaneously hardening said image formingink and forming an ink scum displacing coating on the non-image surfacesof said plate.

4. A method as set forth in claim 3 wherein said planographic printingplate comprises a planographic metal printing plate having an imagethereon formed from a grease base type of ink;

5. A method of treating a planographic printing plate having an imagethereon formed from a grease base type of ink which comprises the stepof applying an aqueous solution of l to 64 ounces of glycerine byvolume, 1 to 8 ounces of sodium sulfate, 1 to 4 ounces of sodiumthiosulfate, and 1 to 4 ounces of citric acid, together with suflicientwater to make one gallon of solution, to the surface of said plate forsimultaneously hardening said image forming ink and forming an ink scumdisplacing coating onthe non-image surfaces of said plate.

6. A method as set forth in claim 5 wherein said planographic printingplate comprises a planographic metal printing plate having an imagethereon formed from a grease base type of ink 7. A combined ink scumremoving and grease base ink hardening etching composition forplanographic printing plates comprising, in the following proportions,20 ounces of glycerine by volume, 1 to 8 ounces of sodium sulfate, 1 to4 ounces of sodium thiosulfate, 1 to 4 ounces of citric acid andsuflicient water to prepare one gallon of solution, said sodiumthiosulfate and citric acid being employed in equal amounts by weight.

8. A combined ink scum removing and grease base ink hardening etchingcomposition for planographic printing plates comprising 4 ounces ofglycerine by volume, 2 ounces of sodium sulfate, 1 ounce of sodiumthiosulfate, 1 ounce of citric acid and suflicient water to bring thevolume of the solution up to one gallon.

9. A method of treating a planographic printing plate having an imagethereon formed from a grease base type of ink which comprises the stepof applying an aqueous solution of 4 ounces of glycerine by volume, 2ounces of sodium sulfate, 1 ounce of sodium thiosulfate and 1 ounce ofcitric acid, together with sufiicient water to make one gallon ofsolution, to the surface of said plate for simultaneously hardening saidimage forming ink and forming an ink scum displacing coating on thenon-image surfaces of said plate.

10. A method as set forth in claim 9 wherein said planographic printingplate comprises a planographic metal printing plate having an imagethereon formed from a grease base type of ink.

11. A dampening composition for planographic paper printing platescomprising, in the following proportions, 12.8 to 64 ounces of glycerineby volum e, lto 16 ounces of sodium sulfate, 1 to 6 ounces of boricacid, V to 3 ounces of gum acacia, and sufficient water to bring thevolume of the solution to one gallon.

12. A dampening composition for. planographic paper printing platescomprising, in the following proportions, 12.8 to 64 ounces of glycerineby volume, 1 to 16 ounces of sodium sulfate, 1 to 6 ounces of boricacid, 1 ounce of gum acacia, and sufficient water to bring the volume ofthe solution to one gallon.

13. A dampening composition for planographic paper printing platescomprising 64 ounces of lycerine by volume, 6 ounces of sodium sulfate.2 ounces of boric acid, V4 to 3 ounces of gum acacia, and suflicientwater to bring the volume of the solution to one gallon.

14. A method of dampening planographic paper printing plates comprisingthe step of treating the non-image portions thereof with an aqueoussolution of 12.8 to 64 ounces of glycerine by volume, 1 to 16 ounces ofsodium sulfate, 2 ounces of boric acid, V ounce of gum acacia and awater drying compound for rendering said non-image portions repellent tolithographic inks, and suflicient water to bring the volume of solutionto one gallon.

15. A method of dampening planographic paper printing plates comprisingthe step of treating the non-image portions thereof with an aqueoussolution of 12.8 to 64 ounces of glycerine by volume, 1 to 16 ounces ofsodium sulfate, 2 ounces of boric acid and V to 3 ounces of gum acaciato render said non-image portions repellent to lith ographic inks, andsufllcient water to bring the volume of solution to one gallon.

16. A method as set forth in claim wherein the planographic paperprinting plate comprises an unbacked, unsized sheet of uncalenderedamyloid parchment paper having a minutely 12 fibrous fine grain surfacecharacterized by having low gloss and low smoothness values.

17. A method of dampening planographic paper printing plates comprisingthe step of treating the non-image portions thereof with an aqueoussolution of 12.8 to 64 ounces of glycerine by volume, 1 to -16 ounces ofsodium sulfate, 1 to 6 ounces of boric acid, and M; to 3 ounces of gumacacia in sufilcient water to make a gallon of solution, to render saidnon-image portions repellent to lithographic inks.

18. A method as set forth in claim 17 wherein the planographic paperprinting plates comprise unbacked, unsized sheets of uncalenderedamyloid parchment paper having a minutely fibrous fine grain surfacecharacterized by having low gloss and low smoothness values.

19. A method of preparing 'a planographic printing plate. for use in anoffset printing process, said plate comprising an unbacked sheet ofuncalendered parchment paper having a greasebase ink image thereon,which comprises the steps of applying an aqueous solution of 1 to 64ounces of glycerine'by volume, 1 to 8 ounces'of sodium sulfate, 1 to 4ounces of sodium thiosulfate and 1 to 4 ounces of citric acid, insufllcient water to make a gallon of solution, to the surface of saidplate to harden said image and form an ink scum displacing coating onthe non-image portions of said plate; and thereafter applying an aqueoussolution of 12.8 to 64 ounces of glycerine by volume, 1 to 16 ounces ofsodium sulfate, 1 to 6 ounces of boric acid and V to 3 ounces of gumacacia, in sufllcient water to make a gallon of solution, to thenon-image portions of said plate to render said portions repellent tolithographic inks.

JAMES FINNO.

No references cited.

1. A COMBINED INK SCUM REMOVING AND GREASE BASE INK HARDENING ETCHINGCOMPOSITION FOR PLANOGRAPHIC PRINTING PLATES COMPRISING, IN THEFOLLOWING PROPORTIONS, 1 TO 64 OUNCES OF GLYCERINE BY VOLUME, 1 TO 8OUNCES OF SODIUM SULFATE, 1 TO 4 OUNCES OF SODIUM THIOSULFATE, 1 TO 4OUNCES OF CITRIC ACID AND SUFFICIENT WATER TO PREPARE ONE GALLON OFSOLUTION, SAID SODIUM THIOSULFATE AND CITRIC ACID BEING EMPLOYED INEQUAL AMOUNTS BY WEIGHT.